A 45-year-old man who signed out a 16-year-old girl from her Pennsylvania school 10 times in the last few months before the two went missing was able to do so because she had changed school documents to list him as her stepfather, according to police. US media reports said the two were in a ‘secretive relationship’, according to court documents. Allentown police issued a missing person alert on Wednesday for Kevin Esterly and Amy Yu. Police also issued a warrant for Esterly’s arrest alleging interference with the custody of a child. School records show Esterly signed Amy out of school 10 times between November 13 and February 9 without her parents’ permission, police said. The girl had altered her student records to list Esterly as her stepfather, said Gary Hammer, of the Colonial Regional Police. Hammer told ABC News the girl’s mother arrived to pick her up at Lehigh Valley Academy on February 9 and school workers said she had left with her stepfather. The shocked woman told them she is a single mother. School workers called police, Hammer said. Amy’s younger brother and mother told WFMZ-TV that the two families met at church years ago and Amy is friends with one of Esterly’s daughters. They have even had Esterly over for dinner. They describe Amy as a well-liked girl with lots of friends who always helped take care of her brother, John. John said after his mother dropped him and Amy off at the bus stop Monday, Amy left and he did not know where she was going. Her mother, Mul Luu, said she came home and discovered Amy’s passport missing along with some cash. Luu said she had discovered text messages between Esterly and her daughter on Amy’s phone, and it sounded like they were in a romantic relationship. Amy’s brother said Esterly seemed like a nice, regular guy, but not any more. Her mother told WFMZ-TV she is praying for her child’s return. “We need her to come back,” John said.